1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to devices and methods for disrupting, collecting, and removing occlusive material from blood vessels and other body lumens.
Thrombosis and atherosclerosis are common ailments which occur in humans and which result from the deposition of thrombus and clot on the walls of blood vessels. When hardened, such deposits are commonly referred to as plaque. Such deposits are most common in the peripheral blood vessels that feed the limbs of the human body and the coronary arteries which feed the heart. Stasis, incompetent valves, and trauma in the venous circulation cause thrombosis, particularly occurring as a deep vein thrombosis in the peripheral vasculature. When such deposits build-up in localized regions of the blood vessel, they can restrict blood flow and cause a serious health risk.
In addition to forming in the natural vasculature, thrombosis is a serious problem in xe2x80x9cartificialxe2x80x9d blood vessels, particularly in peripheral femoral-popliteal and coronary bypass grafts and dialysis access grafts and fistulas. The creation of such artificial blood vessels requires anastomotic attachment at at least one, and usually at at least two, locations in the vasculature. Such sites of an anastomotic attachment are particularly susceptible to thrombus formation due to narrowing caused by intimal hyperplasia, and thrombus formation at these sites is a frequent cause of failure of the implanted graft or fistula. The arterio-venous grafts and fistulas which are used for dialysis access are significantly compromised by thrombosis at the sites of anastomotic attachment and elsewhere. Thrombosis often occurs to such an extent that the graft needs to be replaced within a few years or, in the worst cases, a few months.
A variety of methods have been developed for treating thrombosis and atherosclerosis in the coronary and peripheral vasculature as well as in implanted grafts and fistulas. Such techniques include surgical procedures, such as coronary artery bypass grafting, and minimally invasive procedures, such as angioplasty, atherectomy, transmyocardial revasculaturization, and the like. Of particular interest of the present invention, a variety of techniques generally described as xe2x80x9cthrombectomyxe2x80x9d have been developed. Thrombectomy generally refers to procedures for the removal of relatively soft thrombus and clot from the vasculature. Removal is usually achieved by mechanically disrupting the clot, optionally with the introduction of thrombolytic agents. The disrupted thrombus or clot is then withdrawn through a catheter, typically with a vacuum or mechanical transport device.
Thrombectomy generally differs from angioplasty and atherectomy in the type of occlusive material which is being treated and in the desire to avoid damage to the blood vessel wall. The material removed in most thrombectomy procedures is relatively soft, such as the clot formed in deep vein thrombosis, and is usually not hardened plaque of the type treated by angioplasty in the coronary vasculature. Moreover, it is usually an objective of thrombectomy procedures to have minimum or no deleterious interaction with the blood vessel wall. Ideally, the clot will be disrupted and pulled away from the blood vessel wall with no harmful effect on the wall itself.
While successful thrombectomy procedures have been achieved, most have required comprise between complete removal of the thrombosis and minimum injury to the blood vessel wall. While more aggressive thrombectomy procedures employing rotating blades can be very effective at thrombus removal, they present a significant risk of injury to the blood vessel wall. Alternatively, those which rely primarily on vacuum extraction together with minimum disruption of the thrombus, often fail to achieve sufficient thrombus removal.
For these reasons, it would be desirable to provide improved apparatus, systems, methods, and kits for performing thrombectomy procedures. It is particularly desirable that the present invention provide thrombectomy procedures which are both capable of effective thrombus and clot removal while minimizing the risk of injury to the blood vessel wall. The methods and procedures of the present invention should be suitable for treatment of both arteries and veins within the peripheral, coronary, and cerebral vasculature. Even more particularly, the present invention should provide for the treatment of native and synthetic grafts which are subject to thrombosis and clotting, such as arterio-venous grafts and fistulas, bypass grafts, and the like. In addition to treatment of the vasculature, the methods, systems, devices, and kits of the present invention should also be useful for treating other body lumens which are subject to occlusion and blockage due to the presence of occlusive materials within the lumen. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
U.S. Pat. No. 5,904,698, describes a catheter having an expansible mesh with a blade or electrode for shearing obstructive material which penetrates the mesh when the mesh is expanded in a blood vessel. Other catheters having expansible meshes, cages, and/or shearing elements are described in U.S. Pat. Nos. 5,972,019; 5,954,737; 5,795,322; 5,766,191; 5,556,408; 5,501,408; 5,330,484; 5,116,352; and 5,410,093; and WO 96/01591. Catheters with helical blades and/or Archimedes screws for disrupting and/or transporting clot and thrombus are described in U.S. Pat. Nos. 5,947,985; 5,695,501; 5,681,335; 5,569,277; 5,569,275; 5,334,211; and 5,226,909. Catheters having expansible filters at their distal ends are described in U.S. Pat. No. 4,926,858 and PCT publications WO 99/44542 and WO 99/44510. Other catheters of interest for performing thrombectomy and other procedures are described in U.S. Pat. Nos. 5,928,186; 5,695,507; 5,423,799; 5,419,774; 4,762,130; 4,646,736; and 4,621,636. Techniques for performing thrombectomy are described in Sharafudin and Hicks (1997) JVIR 8: 911-921 and Schmitz-Rode and Gxc3xcnthar (1991) Radiology 180: 135-137.
The present invention provides apparatus, systems, methods, and kits for removing occlusive material from body lumens. While the present invention is particularly suitable for the removal of thrombus and clot from the vasculature, it will also find use in other body lumens, such as the ureter, urethra, fallopian tubes, bile duct, intestines, and the like. The present invention is advantageous in a number of respects. In particular, the present invention provides for effective removal of the occlusive material from the body lumen. Such removal is effective in both achieving a high degree of removal and minimizing the amount of material which is released into the body lumen. This is a particular advantage in treatment of the vasculature where the release of emboli can be a serious risk to the patient. The present invention achieves such effective removal with minimum risk of injury to the luminal wall. As described in detail below, the present invention employs a macerator for breaking up or xe2x80x9cdisruptingxe2x80x9d the thrombus, clot, or other occlusive material, where the macerator is carefully positioned to minimize or prevent contact with and reduce or eliminate the potential for injury to the luminal wall.
In a first aspect, apparatus according to the present invention comprises a catheter for removing the occlusive material from the body lumen. The catheter comprises a catheter body having a proximal end, a distal end, and a lumen therethrough. A radially expansible positioning cage is disposed on the catheter body near its distal end, and a macerator is disposed within the expansible positioning cage. The macerator is configured to disrupt occlusive material within the cage when the cage is expanded against the luminal wall. The macerator is typically a rotating element, such as a helical or other shaped wire which engages and disrupts the occlusive material. Usually, the disrupted material will also be drawn into the catheter body lumen. Alternatively, the disrupted thrombus can be captured in whole or in part by a second catheter usually introduced downstream from the first catheter with the macerator. The second catheter may also comprise a macerator and, in some instances, the two catheters can be similar or identical. In all cases, the disrupted thrombus may be removed through the catheter lumen by aspiration using an external vacuum source and/or a mechanical pump. As a further alternative, a portion of the expansible cage can be provided with a mesh or other filter membrane to permit blood or other luminal flow past the catheter while entrapping the disrupted clot. When the expansible cage is collapsed, the captured clot will be contained, permitting its withdrawal together with the catheter. Often, the xe2x80x9cfilteringxe2x80x9d cage can be used in combination with an aspiration lumen within the catheter itself and/or a second catheter for capturing the disrupted thrombus. Optionally, thrombolytic agents can also be introduced through the catheter to help disrupt the thrombus and clot, and a vacuum and/or mechanical extraction system can be used to help transport the disrupted clot, thrombus, or other occlusive material through the catheter and out of the patient""s body.
The radially expansible positioning cage can take a variety of forms, and will usually be configured to position and maintain the distal end of the catheter body away from the luminal wall, preferably at or near the center region of the body lumen being treated. Usually, the cage will be expansible from an initial width (usually diameter) in the range from 1 mm to 4 mm to an expanded width (diameter) from 2 mm to 40 mm. In some instances, the radially expansible cage will have a resilient but generally uncontrolled diameter, i.e., it will be self-expanding. That is, the cage will simply expand within the body lumen to engage the luminal wall and press against the wall with whatever spring force remains in its structure. In such cases, the cage will usually be initially constrained, e.g., by positioning within an outer tube or sheath, and thereafter released from constraint so that it expands within the body lumen to both anchor and center the catheter therein. Alternatively, and usually preferably, the radially expansible cage will have a selectively adjustable diameter. That is, the size or outer diameter of the cage will be controlled by the user so that the cage can be expanded and deployed against the luminal wall with a desired anchoring force. A variety of specific mechanisms for achieving such controlled expansibility are available, with exemplary systems described below.
The radially expansible positioning cage may have a variety of specific configurations. Most commonly, it will consist of a plurality of wires or filaments arranged in axial, helical, or other circumferentially spaced-apart geometries which provide the desired radial positioning forces while retaining sufficiently large gaps or apertures to permit intrusion of the clot or thrombus. As an alternative to wires, the cage could also employ ribbons, perforated plate structures, and will usually be formed from an elastic material, more usually from a metal having spring memory, such as stainless steel, nitinol, or the like. Alternatively, the cage could be formed from a material which expands and responds to electrical or other stimulus. For example, certain bi-metal structures could be electrically heated to effect expansion. Alternatively, heating at a certain heat memory alloys could also permit selective expansion and contraction of the cage. Other specific designs will also be available.
The macerator may also have a variety of configurations, that will generally be configured to engage and optionally penetrate the occlusive material within the body lumen. Usually, the macerator will have a distal portion which engages the clot and thrombus and which is expansible from an initial width (usually diameter) in the range from 1 mm to 4 mm to an expanded width (diameter) in the range from 2 mm to 35 mm. In the case of thrombus and clot, the macerator will usually be able to penetrate into the mass of thrombus or clot to engage and entangle the fibrin strands therein. By thus xe2x80x9ccapturingxe2x80x9d the thrombus or clot, the macerator can then draw the material away from the luminal wall and break up the material sufficiently so that it may be withdrawn, for example, through the lumen of the catheter, optionally, but not necessarily with mechanical and/or vacuum assistance.
The macerator will usually be radially expansible so that, after the catheter has been centered, the macerator may be deployed and expanded to engage the occlusive material without engaging the luminal wall. While it is possible that the macerator would have a fixed width or diameter (i.e., would be released from constraint to assume its full, unconstrained dimension), the macerator will more usually be capable of being selectively expanded (i.e., the user will be able to selectively expand and collapse the macerator to achieve a desired width or diameter). Most preferably, both the cage and the macerator will be selectively expansible, where the expansion of each can be effected separately from the expansion of the other. That is, in the most preferred embodiments of the present invention, the catheter will have both a positioning cage and a macerator which can each be independently adjusted in their radial width or diameter.
Further preferably, the macerator will be rotatable and/or axially movable to assist in breaking up the occlusive material within the cage and drawing the material into the catheter body. In such cases, the catheter will usually further comprise a drive unit attached or attachable to a proximal end of the catheter body. The drive unit will usually be coupled through a drive cable or shaft to the macerator.
In the most preferred configurations, the macerator will comprise an expansible shaped wire which can be deployed within the positioning cage. The shaped wire may have a generally uniform diameter, but will more usually be non-uniform in diameter, thus being a spiral or other particular geometry. The width of the shaped wire may be adjusted in a variety of ways. For example, two spaced-apart points on the wire may be axially translated relative to each other in order to open or close the helix or other geometry. Alternatively, or additionally, the two spaced-apart points on the shaped wire may be rotated relative to each other in order to achieve expansion and contraction of the wire. Several specific shaped wire macerator designs are presented hereinafter.
In a second aspect, apparatus of the present invention comprises the macerator assemblies. For example, a first embodiment of the macerator comprises a tubular shaft having a proximal end, a distal end, and at least one lumen therethrough. A wire having a distal section and a helical shank is disposed within the tubular shaft so that a distal section of the wire is attached to an exterior location near the distal end of the shaft. The distal section of the wire will be shaped or shapeable so that it can be radially expanded from the tubular shaft to provide a clot disruption structure. In the simplest embodiments, the wire may be expanded to form a simple arc-shaped profile which can be rotated to generate an ovoid path within the clot. Alternatively, the distal section of the wire could have a more complex geometry, such as a helical coil having one, two, three, or more turns on the distal shaft after it is expanded. Other geometries will also be possible. A proximal end of the shank is slidably received in the lumen of the shaft so that the distal section can be radially expanded and contracted by axially translating the shank relative to the shaft. Optionally, the tubular shaft will include only the single lumen which will extend the entire length of the shaft. In that case, the wire will pass into the lumen through a port in the side of the shaft. Preferably, the single internal lumen will have a diameter which is sufficiently large to accommodate both the wire and a separate guidewire, at least over the portions of the shaft where both would be present. In such cases, the internal diameter will usually be at least 0.25 mm, often at least 0.5 mm, preferably at least 1 mm, and sometimes 1.5 mm or larger. Also in such cases, the capture wire will have a diameter in the range from 0.05 mm to 1.5 mm, usually from 0.5 mm to 1.3 mm, at least over that portion of the capture wire which is within the lumen with the guidewire.
In an alternative embodiment, the tubular shaft may include at least two lumens, where the wire is received in a proximal portion of one lumen and the other lumen is configured to receive a guidewire. Usually, the capture wire lumen will terminate proximally of the distal end of the tubular shaft, but the lumen which receives the guidewire will extend the entire length of the shaft.
A second embodiment of the macerator of the present invention comprises a tubular shaft assembly including an outer tube having a proximal end, a distal end, and a lumen therethrough. An inner tube having a proximal end, a distal end, and a lumen therethrough is rotatably and/or slidably received in the lumen of the outer tube, and a wire coil has one end attached to the proximal end of the inner tube and another end attached to the proximal end of the outer tube. Thus, the wire coil can be radially expanded and collapsed by rotating and/or axially translating the inner tube relative to the outer tube.
Both of the macerators just described will find use in combination with any of the catheter systems described earlier in this application.
In another aspect of the present invention, methods for removing occlusive material from a body lumen comprise positioning a macerator so that it is spaced inwardly from (usually centered within) a surrounding wall of the body lumen. The macerator is rotated and/or axially translated to disrupt and optionally capture clot without significant shearing. The disrupted clot may then be withdrawn through a catheter within the body lumen, usually the catheter used to deploy the macerator, or otherwise captured. In the preferred embodiments, the width of the macerator will be adjusted, and the macerator is in the form of a helical wire. In the case of helical wire macerators, width adjustment can be achieved by rotating and/or axially translating spaced-apart points on the wire to achieve a desired helical diameter. Usually, positioning the macerator is achieved by expanding a positioning cage within the body lumen, where the macerator is located within the positioning cage. In such cases, the methods will usually further comprise translating and/or rotating the macerator within the positioning cage.
The present invention still further comprises kits, including a catheter having a macerator near its distal end. The kits will further include instructions for use according to any of the methods set forth above. In addition to the catheter and instructions for use, the kits will usually further comprise packaging, such as a box, pouch, tray, tube, bag, or the like, which holds the catheter and the instructions for use. Usually, the catheter will be maintained sterilely within the package, and the instructions for use will be printed on a separate package insert or piece of paper. Alternatively, the instructions for use may be printed in whole or in part on a portion of the packaging itself.